Widely tunable grating-assisted heterogeneous silicon nitride/polymer waveguide coupler.

A grating-assisted heterogeneous waveguide coupler is designed, fabricated, and demonstrated on a polymer platform. The parallel silicon nitrite core and polymer core are horizontally placed with vertical center alignment accuracy of ±5 nm. The coupler is differentially thermally tunable. The temperature gradient distribution, introduced by offset micro-heaters, is studied by thermal simulations. A total tuning range of 82 nm is demonstrated experimentally.